Could not deliver the message in the time limit specified

Hi,
I’m running Exchange 2003. When I send mail to one particular domain I’m getting not delivered messages as below. I have checked MS KB and none of their recommendations were applicable.

______________________________________________
From: System Administrator
Sent: Thursday, March 29, 2007 12:55 PM
To: user@somewhere.com
Subject: Test Email

Your message did not reach some or all of the intended recipients.

Subject: Test Email
Sent: 27/03/2007 12:48 PM

The following recipient(s) could not be reached:

user@somewhere.com on 29/03/2007 12:55 PM
Could not deliver the message in the time limit specified. Please retry or contact your administrator.

Thanks,
Adam